Description

glDepthFunc specifies the function used to compare each incoming pixel depth value with the depth value present in the depth buffer. The comparison is performed only if depth testing is enabled. (See glEnable​ and glDisable​ of GL_DEPTH_TEST.)

func​ specifies the conditions under which the pixel will be drawn. The comparison functions are as follows:

GL_NEVER

Never passes.

GL_LESS

Passes if the incoming depth value is less than the stored depth value.

GL_EQUAL

Passes if the incoming depth value is equal to the stored depth value.

GL_LEQUAL

Passes if the incoming depth value is less than or equal to the stored depth value.

GL_GREATER

Passes if the incoming depth value is greater than the stored depth value.

GL_NOTEQUAL

Passes if the incoming depth value is not equal to the stored depth value.

GL_GEQUAL

Passes if the incoming depth value is greater than or equal to the stored depth value.

GL_ALWAYS

Always passes.

The initial value of func​ is GL_LESS. Initially, depth testing is disabled. If depth testing is disabled or if no depth buffer exists, it is as if the depth test always passes.

Notes

Even if the depth buffer exists and the depth mask is non-zero, the depth buffer is not updated if the depth test is disabled. In order to unconditionally write to the depth buffer, the depth test should be enabled and set to GL_ALWAYS.